DISAFA, Microbiology and Food Technology Sector, University of Turin, Grugliasco, Italy.
SC Controllo Alimenti e Igiene delle Produzioni, Istituto Zooprofilattico Sperimentale PVL, Turin, Italy.
Appl Environ Microbiol. 2018 Jan 17;84(3). doi: 10.1128/AEM.02120-17. Print 2018 Feb 1.
Changes in the microbial gene content and abundance can be analyzed to detect shifts in the microbiota composition due to the use of a starter culture in the food fermentation process, with the consequent shift of key metabolic pathways directly connected with product acceptance. Meat fermentation is a complex process involving microbes that metabolize the main components in meat. The breakdown of carbohydrates, proteins, and lipids can lead to the formation of volatile organic compounds (VOCs) that can drastically affect the organoleptic characteristics of the final products. The present meta-analysis, performed with the shotgun DNA metagenomic approach, focuses on studying the microbiota and its gene content in an Italian fermented sausage produced by using a commercial starter culture (a mix of and ), with the aim to discover the connections between the microbiota, microbiome, and the release of volatile metabolites during ripening. The inoculated fermentation with the starter culture limited the development of and reduced the microbial diversity compared to that from spontaneous fermentation. KEGG database genes associated with the reduction of acetaldehyde to ethanol (EC 1.1.1.1), acetyl phosphate to acetate (EC 2.7.2.1), and 2,3-butanediol to acetoin (EC 1.1.1.4) were most abundant in inoculated samples (I) compared to those in spontaneous fermentation samples (S). The volatilome profiles were highly consistent with the abundance of the genes; elevated acetic acid (1,173.85 μg/kg), ethyl acetate (251.58 μg/kg), and acetoin (1,100.19 μg/kg) were observed in the presence of the starters at the end of fermentation. Significant differences were found in the liking of samples based on flavor and odor, suggesting a higher preference by consumers for the spontaneous fermentation samples. Inoculated samples exhibited the lowest scores for the liking data, which were clearly associated with the highest concentration of acetic acid. We present an advance in the understanding of meat fermentation by coupling DNA sequencing metagenomics and metabolomics approaches to describe the microbial function during this process. Very few studies using this global approach have been dedicated to food, and none have examined sausage fermentation, underlying the originality of the study. The starter culture drastically affected the organoleptic properties of the products. This finding underlines the importance of starter culture selection that takes into consideration the functional characteristics of the microorganism to optimize production efficiency and product quality.
微生物基因组成和丰度的变化可以被分析出来，以检测食品发酵过程中使用起始培养物后微生物群落组成的变化，这会导致与产品接受度直接相关的关键代谢途径发生变化。肉类发酵是一个复杂的过程，涉及到代谢肉中主要成分的微生物。碳水化合物、蛋白质和脂肪的分解会导致挥发性有机化合物（VOC）的形成，这些化合物会极大地影响最终产品的感官特性。本研究采用高通量 DNA 宏基因组方法，重点研究了使用商业起始培养物（一种 和 的混合物）生产的意大利发酵香肠中的微生物群落及其基因组成，目的是发现微生物群落、宏基因组与挥发性代谢物在成熟过程中的释放之间的联系。起始培养物的接种发酵限制了 和 的发展，并降低了与自发发酵相比的微生物多样性。KEGG 数据库中与乙醛还原为乙醇（EC 1.1.1.1）、乙酰磷酸转化为乙酸（EC 2.7.2.1）和 2,3-丁二醇转化为乙酰基丁酮（EC 1.1.1.4）相关的基因在接种样品（I）中比在自发发酵样品（S）中更为丰富。挥发组图谱与基因的丰度高度一致；发酵结束时，接种物存在时，观察到乙酸（1,173.85 μg/kg）、乙酸乙酯（251.58 μg/kg）和乙酰基丁酮（1,100.19 μg/kg）的含量升高。基于风味和气味对样品的喜好程度存在显著差异，这表明消费者更喜欢自发发酵的样品。接种样品的喜好数据得分最低，这与乙酸的最高浓度明显相关。我们通过将 DNA 测序宏基因组学和代谢组学方法相结合来描述该过程中的微生物功能，从而在理解肉类发酵方面取得了进展。使用这种全局方法的研究很少专门针对食品进行，也没有研究香肠发酵，这突出了该研究的原创性。起始培养物极大地影响了产品的感官特性。这一发现强调了选择起始培养物的重要性，需要考虑微生物的功能特性，以优化生产效率和产品质量。
